The carbon cost of breakfast at COP26

A French minister told people to eat fewer croissants at this year’s COP26 summit, after the menu said the carbon cost of the pastry was higher than that of a bacon roll, even if it was made without butter. Tim Harford investigates whether this claim could be true, and how the effect of food on climate change can be measured.(Image: Continental breakfast with coffee and croissants: Getty/Cris Cantón)